Positive cement placement tool

ABSTRACT

Cement slurry injected or delivered into a wellbore during cementing operations can be positively placed with a positive placement tool. The tool can be located along to a casing string and have a mandrel with a tubular centralizer sleeve rotatably fit thereabout, the centralizer sleeve having one or more radial guides extending longitudinally thereon. Reciprocal stroking of the casing string causes a helical drive arrangement, acting between the mandrel and the centralizer sleeve, to drive the centralizer sleeve longitudinally along a length of the mandrel while concurrently rotating the centralizer sleeve thereabout. The rotational movement of the centralizer sleeve provides positive impetus to force the injected cement slurry fully about the casing string.

FIELD

Embodiments disclosed herein relate to centralizers and moreparticularly to centralizers that are controllably rotatable forpositively displacing annular cement injected downhole during cementingoperations.

BACKGROUND

It is common practice in the oil and gas industry to cement casingwithin a wellbore, after drilling the wellbore to depth, by introducingcement into an annular space between the wellbore and the casing. Thisprocess of cementing is often completed for various reasons, includingrestricting fluid movement between zones in a formation and to bond andsupport the casing within the wellbore.

Cementing is typically performed by injecting and circulating cementslurry through an internal bore of the casing string from the surface,and into the annulus through a valve or casing shoe located at thebottom of the casing string. Often, casing strings can also incorporatefloat shoes or float collars to prevent backflow of the cement slurryduring cementing.

To ensure proper bonding between the casing and the wellbore, the casingstring can be centralized within the wellbore, providing an annulushaving an uniform thickness. In ideal circumstances, the wellbore andthe casing string would be substantially concentric.

In vertical wellbores, centralizers can be used to provide sufficientannular space between the casing and the wellbore for the cement slurryduring cementing operations.

In horizontal wellbores, or wellbores having a laterally extendingsection, the force of gravity acting on the casing string causes thecasing string to rest or lay on or adjacent a bottom of the wellbore.Further, during drilling, portions of the bottom of the wellbore may bewashed away to form small pockets or cavities that can lie underneaththe casing string, along the bottom of the wellbore wall. Accordingly,there may be portions along a casing string in a horizontal wellborethat may not have sufficient annular space between the casing string andthe bottom surface of the wellbore to permit a satisfactory cementplacement and bonding.

As with vertical wellbores, centralizers can be deployed along thecasing string for use in the laterally extending sections or alonghorizontal wellbores to space the casing from the bottom of thewellbore. However, the injection of the cement slurry into the annularspace solely relies on fluid dynamics, the cement taking the path ofleast resistance, tending to travel along the open top and sides of thecasing string. As a result there can be multiple locations along thebottom of a horizontal or lateral section of the wellbore where theextent of bonding is less than optimal.

Further, and due to recent regulations for increasing environmentalsafety, many regulatory bodies now require bond logs to evidencesufficient bonding between the casing and the wellbore.

Accordingly, there is a need to ensure that a sufficient amount ofcement is placed between the casing and the walls of a wellbore,particularly between the casing and the bottom surface of a horizontalwellbore, to achieve sufficient bonding therebetween for satisfying thecompletion objectives, regulatory requirements and permitting furtherdownhole operations.

SUMMARY

Centralizers, being able to either freely rotate about a casing stringor not rotate at all, cannot mechanically provide additional or positiveimpetus to move, positively direct, or otherwise force cement slurry,injected into a laterally extending or horizontal section of a wellbore,about and along the casing string, particularly under the casing string.

A positive cement placement tool, disposed along a casing string inlaterally extending or horizontal sections of a wellbore, canmechanically provide a positive impetus for positively directing orforcing the injected cement slurry about and along a casing string. Inembodiments, the tool can comprise a centralizer, which can be actuatedto rotate about the casing string, for forcing the injected cementslurry around and along the casing string. In embodiments, the tool canbe actuated to rotate in a first direction and then in a second oppositedirection by the reciprocal uphole and downhole stroking of the casingstring, for mechanically providing positive impetus to force the cementslurry around and along the casing string.

In a broad aspect, a positive placement tool can be located along acasing string for placing a cement slurry about the casing string. Thecement placement tool can comprise a mandrel adapted for location withinthe casing string, a centralizer sleeve fit concentrically and movableon the mandrel, and a helical drive arrangement acting between themandrel and the centralizer sleeve for actuating the centralizer sleevealong a length of the mandrel while rotating the centralizer sleevethereabout. The centralizer sleeve further comprises one or more radialguides extending generally longitudinally along the sleeve for engagingthe cement slurry.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side view of an embodiment of the positive placement toolillustrating a mandrel adapted to be located along to a casing string, arotatable centralizer, and helical grooves on the mandrel forming aportion of a helical drive arrangement;

FIG. 1B is a side view of another embodiment of the positive placementtool, illustrating a mandrel sleeve secured to a section of a casingstring, a rotatable centralizer, and helical grooves on the mandrelsleeve forming a portion of a helical drive arrangement;

FIG. 2A is a side cross-sectional view of FIG. 1A, illustrating thebody, a centralizer sleeve moveably supported about the mandrel, and thehelical drive arrangement comprising a guide pin extending through thecentralizer sleeve and a helical groove along a surface of the mandrelfor accepting the guide pin;

FIG. 2B is a side cross-sectional view of FIG. 1B, illustrating themandrel sleeve secured to a section of a casing string by set screws, acentralizer sleeve moveably supported about the mandrel sleeve, and thehelical drive arrangement comprising a guide pin extending through thecentralizer sleeve and helical grooves along a surface of the mandrelfor accepting the guide pin;

FIG. 3 is a partial cross-sectional view of the embodiment shown in FIG.1A, illustrating an embodiment of the helical drive arrangement betweenthe mandrel and the rotatable centralizer, the helical drivearrangement;

FIG. 4 is plan cross-sectional view of a FIG. 3, illustrating threeguide pins engaging the helical groove;

FIG. 5A is a perspective view of an embodiment of a rotatablecentralizer, illustrating a centralizer sleeve having three radialhelical guides;

FIG. 5B is a perspective view of an embodiment of a rotatablecentralizer, illustrating a centralizer sleeve having four radialguides, each guide having a narrow width at about a midpoint thereof;

FIG. 5C is a perspective view of an embodiment of a rotatablecentralizer, illustrating a centralizer sleeve having four radialguides, each guide having opposing ends that flare;

FIG. 6A is a drawing illustrating a positive cement placement tool beingstroked downhole and causing a centralizer sleeve to be rotated in afirst direction;

FIG. 6B is a drawing illustrating the placement tool of FIG. 6B beingstroked uphole for causing the centralizer sleeve to be rotated in asecond opposite direction;

FIGS. 7A to 7C is a series of cross-sectional schematic drawings of anembodiment of a positive cement placement tool placed within ahorizontal wellbore and being stroked downhole during the injection of acement slurry into a wellbore;

FIG. 7A illustrates an initial injection of the cement slurry, thecement slurry filling an upper portion of the wellbore;

FIG. 7B illustrates the beginning of the downhole stroke of the casingstring and the cement slurry being forced about the tool and casingstring; and

FIG. 7C illustrates the cement slurry after the placement tool hasforced the cement slurry about the tool and the casing string.

DESCRIPTION

A positive cement placement tool can be incorporated or located within acasing string and run downhole for use during cementing operations.During cementing operations, and as cement slurry is injected orotherwise delivered into the wellbore, the positive cement placementtool can be actuated by reciprocating the casing string. A stroking thecasing string, alternating between an uphole and a downhole movement,positively directs or otherwise forces the cement slurry about and alongthe tool. The cement slurry is also distributed along the casing string.Typically, a plurality of tools are spaced along the casing string.

Embodiments of a positive cement placement tool described hereingenerally comprise a tubular mandrel having a controllably rotatablecentralizer positioned thereabout. The casing string is reciprocated,also reciprocating the mandrel. A helical drive mechanism, positionedbetween the mandrel and the centralizer, actuates or drives thecentralizer to move relatively along a length of the mandrel and toconcurrently rotate thereabout. The centralizer rotates in a firstdirection when the casing string is stroked uphole, and rotates in anopposite second direction when the casing string is stroked downhole.The rotation of the centralizer imparts a positive and mechanicalimpetus to force the cement slurry about the tool.

In more detail, and with reference to FIGS. 1A and 1B, a positive cementplacement tool 10 comprises a tubular mandrel 15. One or more mandrels15 are formed integral with or are secured within, and spaced along, acasing string (see FIG. 6A) for providing one or more centralizerlocations therealong. A tubular centralizer 20 is concentrically fitabout to each tubular mandrel 15 and operationally actuable by a helicaldrive arrangement 25, for reciprocal movement therealong and concurrentrotational movement thereabout.

The tubular centralizer 20 comprises a tubular centralizer sleeve 21 andone or more fins or radial guides 30 extending generally axially along alength of the sleeve 21, and extending radially from an outer surface 35thereof. Each radial guide 30 spaces the centralizer sleeve 21 from thewellbore, forming a space for receipt of cement slurry therein. Whenrotated, the guides engage the cement slurry for movement from oneradial location and forcing the cement slurry further andcircumferentially about tool 10. The form of the radial guides 30 caninclude axially-extending through helical-extending. Typically acentralizer has three or more radial guides, spaced circumferentiallythereabout.

In an embodiment, the one or more radial guides 30 can be two or moreradial guides spaced apart circumferentially along the outer surface 35of the centralizer sleeve 21.

As shown in FIG. 1A, and in an embodiment, the tubular mandrel 15 can bea section of casing 40 adapted to be incorporated as part of the casingstring. As shown, the section of casing 40 is secured within the casingstring such as by threadable attachment uphole and downhole thereof.

In another embodiment, and as shown in FIG. 1B, the mandrel 15 can be amandrel sleeve 45 having a sleeve bore extending longitudinallytherethrough, for concentrically fitting about a tubing section of thecasing string.

In the embodiment illustrated in FIG. 1B, the mandrel sleeve 45 isslidably fit concentrically about a section 50 of the casing string. Themandrel sleeve 45 is rotationally secured to the casing string section50 and fixed longitudinally therealong. Set screws 60 can be insertedthrough a plurality of holes 55, spaced apart circumferentially aboutthe outer surface of the mandrel sleeve 45 and extend radiallytherethrough to engage the casing section 50. Although not shown, inother embodiments, the mandrel sleeve 45 can be secured to the casingstring by other attachment means, such as one or more locking collars.

Generally, the helical drive arrangement 25 cooperates between themandrel 15 and the centralizer 20 and controllably actuates thecentralizer 20 to rotate about the mandrel 15 as the mandrel 15 movestherethrough, enabling the centralizer 20 to be controllably actuablelongitudinally and rotationally relative to the mandrel 15 and thecasing string.

With reference to FIGS. 2A and 2B, the helical drive arrangement 25comprises one or more helical slots or grooves 65 cooperating with oneor more guide pins 70 for guiding the centralizer 20 rotationally andlongitudinally relative to the mandrel 15. In an embodiment, the one ormore helical grooves 65 are formed on an outer surface 75 of the mandrel15. In an alternate embodiment, the one or more helical grooves 65 canbe formed on an inner surface of the centralizer (not shown). The pins70 are formed on the opposing and complementary component, either thecentralizer 20 or mandrel 15 respectively. Particularly, the one or moreguide pins 70 extend radially from the other of the inner surface of thecentralizer to slots in the mandrel 15 or, alternatively, from the outersurface of the mandrel 15 where the one or more helical grooves 65 areformed on the inner surface of the centralizer 20. An embodiment of thehelical drive arrangement is disclosed in U.S. Pat. No. 8,973,682.

With reference to the embodiment of FIGS. 3 and 4, the helical drivearrangement 25 comprises at least one helical groove 65 along the outersurface 75 of the mandrel 15, and three guide pins 70,70,70, equallyspaced apart and extending radially inwardly from an inner surface 80 ofthe centralizer 20. Each of the three guide pins 70,70,70 extend fromthe inner surface of the centralizer 20 and is received in the at leastone helical groove 65. Accordingly, as the guide pins 70,70,70 arelocated within the helical groove 65, the guide pins 70,70,70 follow atravel path defined by the at least one helical groove 65, causing thecentralizer 20 to travel along the length of the mandrel 15 whileconcurrently rotating thereabout.

Thus, stroking the casing string in one direction will cause thecentralizer 20 to rotate about the mandrel 15 in a first direction,providing positive impetus for forcing the cement slurry ahead of theradial guides 30 from one circumferential location to anothercircumferential location about the tool 10. The longitudinal travel ofthe casing string and of the centralizer 20 along the mandrel 15 of tool10 provides positive impetus for forcing or pushing the cement slurryaxially along the tool 10 and along the casing string.

The stroking of the casing string in the opposite direction will drivethe centralizer 20 to rotate about the mandrel 15 in a second oppositedirection, once again forcing the cement slurry about the tool 10.Continued longitudinal travel of the centralizer along the mandrel 15 ofthe tool 10 in the opposite direction forces the cement slurry to bepushed along the tool 10 and the casing string in the oppositedirection.

In an embodiment, the guide pins 70 are fastened securely to extendradially inwardly. In an embodiment, the pins 70 are welded to the innersurface 80 of the centralizer. In an alternate embodiment, and as shownin FIGS. 1A and 1B, holes 90 for the guide pins 70 can be drilledthrough the centralizer 20, guide pins 70 inserted therethrough, andthen the pins 70 welded to the centralizer 20.

The tolerance in the annulus between the centralizer 20 and the mandrel15 is sufficiently tight such that each guide pin 70 remains radiallyengaged in its corresponding helical groove 65 when the tool 10 isassembled and actuated. Further, in the embodiment of FIG. 1B, where themandrel 15 comprises the tubular mandrel sleeve 45 (see FIG. 1B), theattachment means used to secure the sleeve 45 to the section 50 of thecasing string, such as the set screws 60, are compatible to avoidseparation of the sleeve 45 from the casing string during use. Setscrews are immune to the reactive torque provided by the action of thehelical drive 25 and direction of the helical groove 65.

Referring back to FIG. 3, a pitch of the helical groove 65 may beuniform along the path of the helical groove 65, or may vary to changethe speed of rotation of the centralizer 20 (not shown). As shown, thepitch of the helical groove can be about 45°.

With reference to FIG. 5A, in an embodiment, the centralizer 20comprises a tubular centralizer sleeve 21 and one or more radial guides30, such as a helical guide, extending along and advancing helicallyabout a length of the sleeve 21. Each radial guide extends radially awayfrom the outer surface 35 thereof for spacing the centralizer sleeve 21from the wellbore and engaging a portion of the cement slurry thereaboutand providing a positive impetus for forcing the cement slurry about thetool 10. Simply, as the one or more radial guide 30 engages the cementslurry, the cement slurry is forced to travel circumferentially aboutand along the centralizer 20.

As shown, each radial guide further comprises two lateral sides 31 a,31b for engaging the cement slurry and a top 32. As the centralizer 20rotates in both the clockwise and counterclockwise directions, theradial guides provide the same positive impetus for forcing the cementslurry underneath and about the casing string. Accordingly, lateral side31 a can engage the cement slurry when the centralizer 20 rotates in afirst direction and lateral side 31 b can engage the cement slurry whenthe centralizer 20 rotates in a second opposite direction.

The one or more guides 30 can be two or more guides 30,30 equally spacedapart circumferentially along the outer surface 35 of the centralizersleeve 21. The lateral sides 31 a,31 b can further have a longitudinalprofile for defining a cavity for urging or conveying the cement slurryunderneath and about the centralizer 20.

In an embodiment, and shown in FIG. 5A, the lateral sides 31 a,31 b canhave a helical profile extending longitudinally and helically about thecentralizer sleeve 21. In another embodiment, and as shown in FIG. 5B,the lateral sides 31 a,31 b can have a concaved longitudinal profile. Inanother embodiment, and shown in FIG. 5C, each lateral side 31 a,31 bcan have a longitudinal profile that can flare to form a scoop 32 at anend.

In Operation

With reference to FIGS. 6A and 6B, in operation, at least one tool 10and typically a plurality of tools 10, 10 . . . can be located, placedor otherwise disposed along a casing string 100 and run into ahorizontal wellbore 110. The casing string 100 and the wellbore 110 forman annulus 115 therebetween. During cementing operations, as the cementslurry is injected or otherwise delivered into the annulus 115 betweenthe casing string 100 and the wellbore 110, the casing string 100 can beaxially reciprocated, causing the at least one tool 10 to rotate ineither a first or second direction depending on the direction of thestroke.

As shown in FIG. 6A, in an embodiment, a downhole axial movement of thecasing string 100 causes the centralizers 20,20 to travel, in a relativesense, in the uphole direction along the mandrel 15 and concurrentlyrotate in a clockwise direction. The clockwise rotation of thecentralizer 20,20 and a paddle-like effect of the guides 30 forces atleast some of the cement slurry that is available at one circumferentialportion of the annulus 115 to another circumferential location betweenthe casing string 100 and the wellbore 110. At least some of the cementslurry in the annulus 115 that might have settled above a laterallyextending portion of the casing string 100 can be forced to anothercircumferential location along the tool 10.

Similarly, and as shown in FIG. 6B, an uphole axial movement of thecasing string 100 causes the centralizers 20,20 to travel in thedownhole direction and concurrently rotate in a counterclockwisedirection. The counterclockwise rotation of the centralizers 20,20forces the cement slurry circumferentially about the centralizers 20,20.

Each reciprocal stroking causes the centralizer 20, 20 to rotate in aclockwise direction and then in a counterclockwise direction, providingpositive impetus and forcing the cement slurry about the tools 10,10 andthe casing string 100. As shown, while the centralizer 20 of each tool10 may travel along its mandrel 15, the relative position of thecentralizer 20 within the wellbore 110 remains substantially the samewithin the wellbore 110.

For example, and with reference to FIGS. 7A to 7C, as cement slurry CSis injected into the annulus 115, the cement slurry CS enters into thehorizontal wellbore 110 and begins to fill the annulus 115. As thecasing string 100 is reciprocated (alternately stroked uphole anddownhole) the centralizers are actuated to rotate about the casingstring 100.

As shown, and in an embodiment, as the casing string 100 is strokeddownhole, the centralizers can rotate in a clockwise direction. At thebeginning of the downhole stroke, upper portions of the wellbore 110 arefilled in the cement slurry, while a portion of the wellbore 110 belowthe tool and casing string may not be so filled (See FIG. 7A). Withreference to FIG. 7B, as the centralizer rotates clockwise, the radialguides 30 a,30 b,30 c forces the cement slurry from the upper portionsof the wellbore 110 around the tool 10 and casing string 100. As radialguide 30 a approaches the upper portion of the wellbore 110, cementslurry fills the annular space between radial guides 30 a and 30 c, allthe while, radial guide 30 b continues to force cement slurry towardsthe bottom portion of the wellbore 110.

As shown in FIG. 7C, continued rotation of the radial guides 30 a,30b,30 c results in the forcible placement of the cement slurry about thecasing string 100, ensuring that there is a sufficient amount cementslurry CS surrounding the casing string 100 for proper cement bonding tothe wellbore 110.

In embodiments, the casing string 100 can be manipulated within thewellbore 110 for relocating the spaced tools 10 along the wellbore 110to further distribute the cement slurry therealong and therebetween. Thetools 10 can be moved further uphole or downhole to repeat the processof forcing the cement slurry about the tools 10 and casing string 100.

Example

For a 8¼ inch wellbore, a casing having an outer diameter of about 7inches can be used as part of the casing string. The casing string canbe made up of a plurality of casing sections, each section having alength of about 11½ feet.

A mandrel sleeve having an outer diameter of about 7.6 inches, an innerdiameter of about 7.1 inches and a length of about 10 feet, can be fitconcentrically about and secured to a casing section using fasteningmeans, such as a plurality of set screws as described above, or alocking collar having similar dimensions as the sleeve.

The 7.6 inch outer diameter of the sleeve provides sufficient materialto mill out a 0.2 inch helical groove on its outer surface while stillproviding sufficient material to maintain structural integrity of thesleeve.

A centralizer having a length of about 5 feet can be manufactured tohave an inner diameter of at least about 7.6 inches, so that it can beconcentrically fit about the sleeve, and have a maximum outer diameterof about 8¼ inches, so that it can concentrically fit within thewellbore. The guides for engaging the cement slurry can then be milledout from the centralizer. The depth of the guides can be varied topermit the tool to fit within a wellbore having various diameters.

In an embodiment, holes can be tapped along the outer surface of thecentralizer, and 1 inch pins of about 0.5 inches in length can beinserted therethrough and then welded into place.

Such an embodiment will provide about two and a half rotations of thecentralizer per stroke in either the uphole or downhole direction,ensuring positive placement of cement slurry about and along the casingstring during cementing.

1. A positive placement tool located along a casing string for placing acement slurry about the casing string within a wellbore comprising: amandrel adapted for location within the casing string; a centralizersleeve fit concentrically and movable on the mandrel, the sleeve havingone or more radial guides extending generally longitudinally along thesleeve; and a helical drive arrangement acting between the mandrel andthe centralizer sleeve for actuating the centralizer sleeve along alength of the mandrel while rotating the centralizer sleeve thereabout.2. The positive placement tool of claim 1, wherein the one or moreradial guides further comprises two or more radial guides spaced apartcircumferentially along an outer surface of the centralizer sleeve. 3.The positive placement tool of claim 1, wherein the one or more radialguides has a profile for urging the cement slurry underneath the casingstring.
 4. The positive placement tool of claim 3, wherein the profileof each of the one or more radial guides defines a cavity for conveyingcement slurry.
 5. The positive placement tool of claim 3, wherein theprofile is a helical profile extending longitudinally and helicallyabout the centralizer sleeve.
 6. The positive placement tool of claim 1,wherein the mandrel is a mandrel sleeve having a bore extendingtherethrough and adapted for receiving the casing string therethrough,further comprising attachment means for securing the mandrel sleeve tothe casing string.
 7. The positive placement tool of claim 6 wherein theattachment means further comprises set screws.
 8. The positive placementtool of claim 1, wherein the helical drive arrangement furthercomprises: at least one helical groove in one or the other of themandrel or the centralizer sleeve; and at least one guide pin extendingfrom the other of the centralizer sleeve or mandrel respectively, eachguide pin corresponding to and arranged for engaging the helical grooveso as to cause the centralizer sleeve to rotate in a first direction andthen in an opposite direction as the centralizer sleeve travels upholeand downhole along the mandrel.
 9. The positive placement tool of claim8, wherein the at least one helical groove and the at least one guidepin are two or more corresponding guide pins and helical grooves, eachbeing equally spaced apart circumferentially about the mandrel.
 10. Amethod of injecting a cement slurry into a wellbore using a casingstring comprising: securing at least one cement placement tool along thecasing string, each placement tool having a centralizer sleeve thereon,the centralizer sleeve having one or more radial guides extendingtherefrom; running the casing string, having the at least one placementtool, into the wellbore and forming an annulus therebetween; injecting acement slurry into the annulus; and driving the centralizer sleeverotatably for engaging cement slurry at one circumferential locationabout the casing string and forcing at least some of the cement slurryto another circumferential location between the casing string and thewellbore.
 11. The method of claim 10, wherein the driving of thecentralizer sleeve about the casing string further comprisesmanipulating the casing string.
 12. The method of claim 10, wherein thedriving of the centralizer sleeve about the casing string furthercomprises stroking the casing string uphole and downhole.
 13. The methodof claim 10, wherein the driving of the centralizer sleeve about thecasing string further comprises actuating a helical drive between thecasing string and the centralizer sleeve for rotating the centralizersleeve first in one direction and then in the opposing direction. 14.The method of claim 10, wherein the driving of the centralizer sleeveabout the casing string further comprises actuating a helical drivebetween the casing string and the centralizer sleeve by stroking thecasing string downhole for rotating the centralizer sleeve in onedirection and stroking the casing string uphole for rotating thecentralizer sleeve in the opposing direction.
 15. The method of claim12, wherein stroking the casing string uphole rotates the centralizer ina clockwise direction, and wherein stroking the casing string downholerotates the centralizer in a counterclockwise direction.